Method of hardening steel.



inch.

.steel of any WILLIAM PAINTER, OF ALLEGHENY, PENNSYLVANIA.

METHOD OF HARDENING STEEL.

Specification of Letters Patent.

Patented March 17, 1908.

Application filed April 13, 1907. Serial No. 363,099.

To all whom it may concern.

Be it known that I, VVILLIAM A. PAINTER, of Allegheny, in the county ofAllegheny and State of Pennsylvania, have invented certain new anduseful Improvements in Methods of Hardening Steel, of which thefollowing is a specification.

.My invention relates to a new and improved method of hardening steeland more particularly to a new method of hardening cast or tool steel,whereby a piece of such size and configuration may be hardened at one ormore points or portions and the balance left soft or unhardened. ','II1carrying out 'my method .of hardening the piece of steel to be treatedis first partially inclosed or shielded by a flexible covering of anysuitable material that will stand a hardening temperature. I prefer toemploy thin sheet iron or thin pieces or sheets of steel for theprotecting material. In practice thethickness of this flexible'coveringmaterial varies from .004 to t, of an -I.I1 no case should thethicknessof the material be such as to prevent a practically uniform heating ofthe article while in its cover and a quick cooling of the prote'ctedportion or portions. In other words the thickness of the coveringemployed should be such as not to prevent a graduated heating and agraduated cooling of the piece being treated, whereby a wide variance intemperature producing a strain between the exposed and covered parts -isavoided. A coveringformed of thick or rigid plates or plates so .thickas to be rigid or vice versa would produce such a variance intemperature between the protected and unprotected I arts that a propergraduated tempering or hardening of the parts could not be effected. Theemployment of thick lates would cause a contraction of the metal andconsequently a strain or crack at the line of juncture of the hardenedand unhardened portions.

The coolingof the protected portion or portions should be qluick asstated, butthe said portions will coo somewhat more slowly than theexposed portion or portions. This will prevent any undue strains in themetal. This shield or covering covers only that portion or portions ofthe article that are to re-' :nain soft, while the portion or portionsto be hardened are left exposed. The covering being preferably thinflexible metal may be readily applied to an article of any size orshape, and cut or bent in such a manner as and being able to accuratelyAfter the piece being treated to expose the portion or portions of thearticle to be hardened. The sheet or sheets constituting the coveringshould be fitted close to the surface of the article, following thecontour of the article, and are suitably fastened by rivets, wires, orother suitable means.

The next step in the process is to subject the partially. covered orprotected article to the action of a proper hardening heat. This is donein the manner usually followed in hardening steel. The thin coveringdoes not interfere 111 any way in the operation of heat ing the articleto the desired hardening tent perature, the operator having perfectcontrol determine the proper heat. has reached the proper temperaturefor hardening, the piece together with its covering is immediatelyquenched in any suitable cooling-bath, preferably .clear water. Upon theremoval of the covering after the quenching step just described, it willbe found that the exposed portion or portions of the steel will behardened and the protected portion or portions soft.

B the employement of my method of hardening, 'I. practically eliminateall risk of breakage, cracking and warping in the ooeration of hardeningand in addition thereto,

prolong the life of the treated article by having in a finished pieceonly those portions hardened that are desirable to he hardened, that isto say, the working or wearing surfaces, and leaving the other portionor portionssoft. The hardened portions being backed up by the soft steelwill produce in almost every hardened steel article much better resultsthan if the article were hardened throughout as is the prevailingpractice.

While my method is particularly applicable for hardening pieces orarticles of steel of large size, such, for example, as large, diesemployed in the making of silverware, brassware and large sectional diesfor electrical work, it may be advantageously employed for hardening anysize or shape.

By my method of hardening, the operator can define with great accuracythe surfaceto be hardened, even to a 312' of an inch. I For example, acircular area may be hardened around-a square opening or a square areahardened around a circular opening or any irregular shape.

the quenching and the removal of the cover- Under my method, after ingpered or drawn usual manner.

method the color 5 hardened portions the hardened and soft portions.

' ,"What I clann is:

as above described, the steel is tem- With steel treated under my uatedcooling suitable hardness in the will first appear on the defining withaccuracy The herein-described method of hardening in presence of a pieceof steel to implart hardness to a por- 10 tion of the steel, Whic thatportion of the by a thin covering not prevent a graduated heating and agradconsists in protecting piece not to behardened VVithesses1;

of a thickness that will YV. G.

of the piece and leavingiexts thin covering to a temg the piece and itscov- In testimony whereof I aflix'my signature tWo Witnesses. WILLIAM A.PAINTER MARGARET HUGHES,

Do OLITTLE

